Sulfur-containing oligomer and dendrimer of acrylate and preparation methods thereof

ABSTRACT

Sulfur-containing oligomer and dendrimer of acrylate and preparation methods thereof are provided. The sulfur-containing oligomer and dendrimer of acrylate are prepared by reacting monomers A and B in Michael addition reaction.

RELATED APPLICATIONS

This application claims priority to Taiwan Application Serial Number101147813, filed Dec. 17, 2012, which is herein incorporated byreference.

BACKGROUND

1. Technical Field

The disclosure relates to an optical resin having a high refractiveindex and a preparation method thereof. More particularly, thedisclosure relates to a sulfur-containing resin having a high refractiveindex and a preparation method thereof.

2. Description of Related Art

Recently, since organic optical resins have advantages of small density,breaking resistance, and handle easiness, the organic optical resins areused as a substitute of glass and widely used for optical lenses,spectacle lenses, fiber optics, windows, and other transparent objectsfield. However, conventional organic optical resins also have manydefects, such as a low refractive index, a large birefringence, and ahigher chromatic dispersion, poor heat resistance, and poor impactresistance. For overcoming these defects, many researchers try todevelop monomers and resins having a high refractive index (>1.49),optical transparency, high hardness, and high impact toughness.

An optical resin with a high refractive index is prepared mainly byintroducing a functional group having a higher molar refractive index toincrease the refractive index of the optical resin. Introducing a sulfuratom into monomers of optical resins is an effective way to increase therefractive index and decrease the chromatic dispersion of the opticalresin.

SUMMARY

In one aspect, the present invention is directed to a sulfur-containingacrylate oligomer having a high refractive index. The sulfur-containingacrylate oligomer having a chemical structure of B¹-A²-B¹, wherein A²and B¹ respectively have chemical structures below:

and wherein R₁, R₄, R₅ and R₆ are respectively an alkyl group with 1-6carbons, and R₂ and R₃ are respectively an aromatic or a cycloalkylgroup.

In another aspect, the present invention is direct to a modifiedsulfur-containing acrylate oligomer having a high refractive index and achemical structure of B¹′-A²-B¹′, B¹′-A²-B¹″, wherein A², B^(1′) and B¹″respectively have the chemical structures below:

and wherein R₁, R₄, R₅ and R₆ are respectively an alkyl group with 1-6carbons, R₂ and R₃ are respectively an aromatic or a cycloalkyl group,and R₇ is an aromatic group or a heterocylic group having at least adouble bond.

In yet another aspect, the present invention also provides asulfur-containing acrylate dendrimer having a chemical structure of

wherein B¹ and B² randomly distributed on terminals of thesulfur-containing acrylate dendrimer, and the chemical structures of A²,B¹, B², and B³ are shown below:

and wherein R₁, R₄, R₅ and R₆ are respectively an alkyl group with 1-6carbons, and R₂ and R₃ are respectively an aromatic or a cycloalkylgroup.

In yet another aspect, the present invention also provides a modifiedsulfur-containing acrylate dendrimer having a chemical structure of

wherein A2, B¹′, B¹″, B²′, and B³ respectively have chemical structuresbelow:

and wherein R₁, R₄, R₅ and R₆ are respectively an alkyl group with 1-6carbons, R₂ and R₃ are respectively an aromatic or a cycloalkyl group,and R₇ is an aromatic group or a heterocyclic group having at least adouble bond.

Furthermore, the present invention also provides preparation methods othe modified and unmodified sulfur-containing acrylate oligomer anddendrimer.

Accordingly, this invention provides a novel sulfur-containing acrylateoligomer and dendrimer, which can be fast crosslinked by UV light. Thecrosslinked product has a high refractive index, and a thin film thereofhas excellent optical property and high light transparency. Thepreparation methods of the sulfur-containing acrylate oligomer anddendrimer have advantages of using cheap and easily obtained rawmaterials, easy operation, and mild and easy controlling reactionconditions, so that the preparation methods can be easily practice inindustry.

The foregoing presents a simplified summary of the disclosure in orderto provide a basic understanding to the reader. This summary is not anextensive overview of the disclosure and it does not identifykey/critical elements of the present invention or delineate the scope ofthe present invention. Its sole purpose is to present some conceptsdisclosed herein in a simplified form as a prelude to the more detaileddescription that is presented later. Many of the attendant features willbe more readily appreciated as the same becomes better understood byreference to the following detailed description considered in connectionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an infrared vibration spectrum of the monomer B1.

FIG. 2 is a ¹H nuclear magnetic resonance spectrum of the monomer B1.

FIG. 3 is an infrared vibration spectrum of the monomer A1.

FIG. 4 is an infrared vibration spectrum of the monomer A2.

FIG. 5 is an infrared vibration spectrum of the sulfur-containingacrylate oligomer C1.

FIG. 6 is a ¹H nuclear magnetic resonance spectrum of thesulfur-containing acrylate oligomer C1.

FIG. 7 is an infrared vibration spectrum of the sulfur-containingacrylate oligomer C2.

FIG. 8 is a ¹H nuclear magnetic resonance spectrum of thesulfur-containing acrylate oligomer C2.

DETAILED DESCRIPTION

Accordingly, a sulfur-containing acrylate oligomer and dendrimer havinga high refractive index and preparation methods thereof are provided. Inthe following detailed description, for purposes of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of the disclosed embodiments. It will be apparent,however, that one or more embodiments may be practiced without thesespecific details. In other instances, well-known structures and devicesare schematically shown in order to simplify the drawing.

Sulfur-Containing Acrylate Oligomer and Preparation Method Thereof

In one aspect, a sulfur-containing acrylate oligomer having a highrefractive index is provided. The sulfur-containing acrylate oligomerhaving a chemical structure of B¹-A²-B¹, wherein A² and B¹ respectivelyhave chemical structures below:

The R₁, R₄, R₅ and R₆ above are respectively an alkyl group with 1-6carbons. For examples, the R₁ and R₄ are respectively a straight chainalkyl group having 1-4 carbons, and the R₅ and R₆ are respectively astraight chain alkyl group having 2, 4, or 6 carbons.

The R₂ and R₃ above are respectively an aromatic or a cycloalkyl group,

such as

According to an embodiment, the R₂ can be

and the R₃ can be

According to another embodiment, the A² can be

According to yet another embodiment, the B¹ can be

In another aspect, a method of preparing the sulfur-containing acrylateoligomer above is also provided. The method comprises dropwise adding amonomer A into an aprotic solvent containing a monomer B (denoted byA→B) to perform Michael addition until the thiol vibration group (—SH)disappear from the infrared (IR) spectrum, such that thesulfur-containing acrylate oligomer can be obtained. The monomers A andB respectively have chemical structures below:

According to an embodiment, the molar ratio of the monomer A to themonomer B is 1:2.

According to another embodiment, the aprotic solvent can be ether,dichloromethane, chloroform, ethyl acetate, butyl acetate, acetone,methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene,ethylbenzene, methyl ethyl ketone, cyclohexanone, butyl acetate,tetrahydrofuran, or N-methylpyrrolidone.

According to yet another embodiment, the method further comprises addinga catalyst to the aprotic solvent to catalyze the Michael addition. Thecatalyst can be an organic base, such as ethylamine, diethylamine,dimethylamine, triethylamine, tributylamine, triethanolamine, aminoethanol, N, N-diethyl amino ethanol, pyridine, morpholine, imidazole, oraniline.

Sulfur-Containing Acrylate Dendrimer and Preparation Method Thereof

In one aspect, a sulfur-containing acrylate dendrimer having a highrefractive index is provided. The sulfur-containing acrylate dendrimeris polymerized by monomers A and B having chemical structures shownbelow:

The sulfur-containing acrylate dendrimer has a chemical structure shownbelow:

The B¹ and B² in the chemical structure are randomly distributed onterminals of the sulfur-containing acrylate dendrimer. The chemicalstructures of A², B¹, B² and B³ are shown below:

The R₁, R₄, R₅ and R₆ in the chemical structures above are respectivelyan alkyl group with 1-6 carbons. For examples, the R₁ and R₄ arerespectively a straight chain alkyl group having 1-4 carbons, and the R₅and R₆ are respectively a straight chain alkyl group having 2, 4, or 6carbons.

The R₂ and R₃ above are respectively an aromatic or a cycloalkyl group,such as

According to an embodiment, the R₂ can be

and the R₃ can be

According to an embodiment, the molecular weight of thesulfur-containing acrylate dendrimer above can be 1,000-100,000,preferably 2,000-70,000, and more preferably 3,000-50,000. For example,the molecular weight of the sulfur-containing acrylate dendrimer abovecan be 3,000, 5,000, 10,000, 15,000, 20,000, 25,000, 30,000, 35,000,40,000, 45,000 or 50,000.

According to another embodiment, the A² can be

According to yet another embodiment, the B¹, B² and B³ respectively canbe

As understood by persons skilled in the art, there must be someunreacted functional groups existed in the terminals of thesulfur-containing acrylate dendrimer, which represents by the symbols ofB¹ and B² above for the monomer B. In the chemical structures of the B¹and B² above, there are unreacted acrylate groups.

When the molar ratio of the monomer A to the monomer B is 1:0.25 to1:0.67, the monomer A in the sulfur-containing acrylate dendrimer mayalso exist in a form as A¹ having a chemical structure shown below. Inthe chemical structure of A¹ below, there is one unreacted thiol group.

In another aspect, a method of preparing the sulfur-containing acrylatedendrimer above is also provided. The method comprises dropwise addingthe monomer A into an aprotic solvent containing the monomer B (denotedby A→B) or dropwise adding the monomer B into the aprotic solventcontaining the monomer A (denoted by B→A) to perform Michael additionuntil the thiol vibration group (—SH) disappear from the IR spectrum,such that the sulfur-containing acrylate dendrimer can be obtained.

The molar ratio of the monomers A to B can be 1:0.25 to 1:4, such as1:0.5 to 1:2, or 1:1 to 1:2. However, when the monomer A is dropwiseadded into the aprotic solvent containing the monomer B, the molar ratioof the monomers A to B cannot be 1:2. If the molar ratio of the monomersA to B is 1:2, the obtained product will be the sulfur-containingacrylate oligomer above, rather than the sulfur-containing acrylatedendrimer. According to an embodiment, the molar ratio of the monomers Ato B can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3,1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, or 1:1.9.

According to another embodiment, the aprotic solvent can be ether,dichloromethane, chloroform, ethyl acetate, butyl acetate, acetone,methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene,ethylbenzene, methyl ethyl ketone, cyclohexanone, butyl acetate,tetrahydrofuran, or N-methylpyrrolidone.

According to yet another embodiment, the method further comprises addinga catalyst to the aprotic solvent to catalyze the Michael addition. Thecatalyst can be an organic base, such as ethylamine, diethylamine,dimethylamine, triethylamine, tributylamine, triethanolamine, aminoethanol, N, N-diethyl amino ethanol, pyridine, morpholine, imidazole, oraniline.

In light of forgoing, the sulfur-containing acrylate oligomer anddendrimer both are obtained by performing at least one Michael addition.Preferably, the sulfur-containing acrylate oligomer and dendrimer bothare obtained by performing two Michael addition reactions with themonomer, which is molecular weight (M.W.) less than 500. The monomercould, for example, be selected from tri-mercaptoacetate (M1),diisocyanate-capped urethane (M2), diisocyanate-capped urethane (M3),diacrylate (ethylene glycol diacrylate) or dithio compound(4,4′-dimercapto-diphenyl sulfide) in the embodiments.

Modification of Sulfur-Containing Acrylate Oligomer and Dendrimer

A thiol-containing modifier (R₇SH) can be further added into thesulfur-containing acrylate oligomer and dendrimer containing unreactedacrylate groups to react with the unreacted acrylate groups thereof, andthus modify the sulfur-containing acrylate oligomer and dendrimer.Therefore, the common structural feature of the sulfur-containingacrylate oligomer and dendrimer is that some terminal acrylate groupsare capped with —SR₇ structure.

For example, the B¹ moiety of the sulfur-containing acrylate oligomer,B¹-A²-B¹, has two unreacted acrylate groups, which can react with thethiol group of the modifier. The obtained product can be B¹′-A²-B¹′,B¹′-A²-B¹″, or B¹″-A²-B¹″, and the moieties B¹′ and B¹″ respectivelyhave the chemical structure shown below.

Similarly, for the sulfur-containing acrylate dendrimer, the B¹ and B²moieties both have unreacted acrylate groups, which can react with thethiol group of the modifier. For example, the obtained product may havethe chemical structure below.

In the chemical structure of the modified sulfur-containing acrylatedendrimer above, the moiety B¹′, B¹″, and B²′ are randomly distributedon terminals of the modified sulfur-containing acrylate dendrimer. Thechemical structures of the A², B¹′, B¹″, and B³ have been shown above.The chemical structure of B²′ is shown below.

The added equivalent number of the thiol-containing modifier has betterto be less than the equivalent number of the unreacted acrylate groupsof the sulfur-containing acrylate oligomer or dendrimer. For example, ifthe sulfur-containing acrylate oligomer has 4n equivalent number ofacrylate groups, the added equivalent number of the thiol-containingmodifier can be 2n equivalent number. For example, if thesulfur-containing acrylate dendrimer has n equivalent number of acrylategroups, the added equivalent number of the thiol-containing modifier canbe 0.8n equivalent number.

The chemical structure of the thiol-containing modifier is R₇SH. The R₇group can be an aromatic group or a heterocyclic group having at least adouble bond, preferably an aromatic group or a nitrogen-containingheterocyclic group having at least a double bond. Some examples of thethiol-containing modifier are listed in the table below.

Chemical name Chemical structure 2-mercaptobenzothiazole

2-mercapto-2-thiazoline

2-mercapto-5-methyl-1,3,4- thiadiazole

thiophenol

4-methyl thiophenol

triphenylmethyl mercaptan

Accordingly, the modified sulfur-containing acrylate oligomer anddendrimer both are obtained by performing at least two Michael additionreactions. Preferably, the modified sulfur-containing acrylate oligomerand dendrimer both are obtained by performing three Michael additionreactions with the monomer, which is molecular weight (M.W.) less than500. The monomer could, for example, be selected fromtri-mercaptoacetate (M1), diisocyanate-capped urethane (M2),diisocyanate-capped urethane (M3), diacrylate (ethylene glycoldiacrylate) or thiophenol compound (4,4′-dimercapto-diphenyl sulfide orthiophenol) in the embodiments.

Cross-Linking Unmodified and Modified Sulfur-Containing AcrylateOligomer and Dendrimer

A photoinitiator is added into the unmodified or modifiedsulfur-containing acrylate oligomer or dendrimer and then uniformlymixed. The mixture is coated on a substrate to form a thin film. Thethin film is illuminated by UV light to cross link the sulfur-containingacrylate oligomer or dendrimer to form a hard and transparent thin film.

The photoinitiator above can be benzophenone, benzoin,2-hydroxy-2-methyl-1-phenyl-propan-1-one,2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxy cyclohexyl phenylketone, 2, 4, 6-trimethylbenzoyl diphenyl phosphine oxide, or a mixturethereof. According to an embodiment, the photoinitiator can bebenzophenone, 1-hydroxy cyclohexyl phenyl ketone,2-hydroxy-2-methyl-1-phenyl-propan-1-one, or 2, 4, 6-trimethylbenzoyldiphenyl phosphine oxide. The added amount of the photoinitiator isabout 0.1-5 wt %, such as 0.1-3 wt %, based on the total weight of thecomposition.

Embodiment 1 Synthesis of Monomer B1

The synthesis of the monomer B, especially B1, is disclosed. Thesynthesis scheme of the monomer B1, trimethylolpropane triacrylate(TMPTA), is shown below.

13.4 g (0.1 mol) of trimethoxypropane (Sinopharm Chemical Reagent Co.Ltd), 33.16 g (0.36 mol) of thioglycolic acid (Sinopharm ChemicalReagent Co. Ltd), and 1.4 g (3 wt %) of composite salt of4-(methylamino) pyridine (Sinopharm Chemical Reagent Co. Ltd) andmethylbenzenesulfonate (Sinopharm Chemical Reagent Co. Ltd) were addedin a three-necked flask. Under conditions of mechanically stirring,nitrogen atmosphere, and 110° C., the reaction was undergone for 8hours. Then, saturated NaHCO₃ and distilled water were used to wash theproduct. Next, the organic phase solution was dried by anhydrous sodiumsulfate, and then distilled at a reduced pressure to obtain colorlessliquid, i.e. trimethylol propane tri-mercaptoacetate (the intermediateM1). The esterification percentage of the product was 98%, and the yieldof the product was 90%.

In a flask equipped with mechanical stirrer, thermometer, and a constantpressure dropping funnel, 20.4 g (0.12 mol) of ethylene glycoldiacrylate (J&K Scientific LTD.) and 20 mL of tetrahydrofuran were addedand mixed. A solution of 14.24 g (0.04 mol) of trimethylol propanetri-mercaptoacetate (the intermediate M1 above), 0.0364 g (0.1 wt %) oftriethylamine, and 20 mL of tetrahydrofuran (THF) was dropwise addedinto the flask and reacted at room temperature until the vibrationalpeak of thiol group (2570 cm⁻¹) was disappeared in the IR spectrum.Next, the colorless transparent viscous liquid, i.e. the product oftrimethylolpropane triacrylate, was obtained by distillation under areduced pressure.

FIG. 1 is an infrared vibration spectrum of the monomer B1. In FIG. 1,the peaks at 1410 cm⁻¹ and 810 cm⁻¹ were the characteristic vibrationpeaks of the double bond of the acrylate group. The peak at 1732 cm⁻¹was corresponding to the characteristic vibration peak of the carbonylgroup of the acrylate group.

The twin peaks at 1100-1300 cm⁻¹ was corresponding to the characteristicvibration peaks of the thiol group.

FIG. 2 is a ¹H nuclear magnetic resonance spectrum of the monomer B1. InFIG. 2, the chemical shifts at 5.90-6.60 ppm (marked by h, i) are thepeaks of the acrylate group. The chemical shifts at 4.31-4.41 ppm(marked by g) are the peaks of the methylene group next to ester group(—CH₂—OCO—). The chemical shifts at 4.04-4.19 ppm (marked by c) and 3.27ppm (marked by d) are the peaks of the methylene group next to thetertiary carbon and the ester group (—C(CH₂O)₃—OCO). The chemical shiftat 3.27 ppm (marked by d) is the peak of the methylene group of thethioether group (—S—CH₂—COO—). The chemical shifts at 2.68 ppm (markedby e) and 2.90 ppm (marked by f) are the methylene group next to thethioether group (—S—CH₂—CH₂—). Therefore, it can be known that theproduct of this embodiment was trimethylolpropane triacrylate, themonomer B1.

Embodiment 2 Synthesis of Monomer A1

The synthesis of the monomer A, especially A1, is disclosed. Thesynthesis scheme of the monomer A1 is shown below.

17.4 g (0.1 mol) of 2,4-toluene diisocyanate (Sinopharm Chemical ReagentCo. Ltd) and 20 mL of THF were added into a flask equipped withmechanical stirrer, thermometer, and a constant pressure droppingfunnel, and then mixed in an ice bath. Next, a solution of 4.5 g (0.05mol) of 1,4-butanediol (Sinopharm Chemical Reagent Co. Ltd), 0.022 g(0.1 wt %) of dibutyltin dilaurate (DBTL; Sinopharm Chemical Reagent Co.Ltd) and 10 mL of THF was added into the flask, and then stirred andreacted for 2 hours to obtain a diisocyanate-capped urethane (theintermediate M2).

25 g (0.1 mol) of 4,4′-dimercapto-diphenyl sulfide (Zhejiang Shou & FuChemical Co., Ltd.) and 100 mL of THF were added into a flask equippedwith mechanical stirrer, thermometer, and a constant pressure droppingfunnel, and mixed uniformly. The intermediate M2 above was then addedinto the flask to react at room temperature until the vibrational peakof isocyanate (2270 cm⁻¹) was disappeared. After distillation under areduced pressure, a dimercapto-capped thiourethane prepolymer (theproduct A1) in white powder was obtained.

FIG. 3 is an infrared vibration spectrum of the monomer A1. In FIG. 3,the peaks at 3293 cm⁻¹ and 1705 cm⁻¹ are vibrational peaks of urethanegroup and thiourethane group

respectively. The peak at 2553 cm⁻¹ is the vibrational peaks of thiolgroup. The peaks of 1600 cm⁻¹, 1531 cm⁻¹ and 1474 cm⁻¹ arecharacteristic peaks of benzene ring. The peak at 814 cm⁻¹ is thebending vibrational peaks of hydrogen attached to substituted benzene.Therefore, it can be known that the dimercapto-capped thiourethaneprepolymer A1 was synthesized.

Embodiment 3 Synthesis of Monomer A2

The synthesis of the monomer A, especially A2, is disclosed. Thesynthesis scheme of the monomer A2 is shown below.

22.2 g (0.1 mol) of isophorone diisocyanate (Sinopharm Chemical ReagentCo. Ltd) and 30 mL of THF were added into a flask equipped withmechanical stirrer, thermometer, and a constant pressure droppingfunnel, and then uniformly mixed in an ice bath. A solution of 4.5 g(0.05 mol) of 1, 4-butanediol (Sinopharm Chemical Reagent Co. Ltd),0.027 g (0.1 wt %) of DBTL (Sinopharm Chemical Reagent Co. Ltd), and 10mL of THF was added and stirred for 2 hours to obtain adiisocyanate-capped urethane (the intermediate M3).

25 g (0.1 mol) of 4,4′-dimercapto-diphenyl sulfide (Zhejiang Shou & FuChemical Co., Ltd.) and 100 mL of THF were added into a flask equippedwith mechanical stirrer, thermometer, and a constant pressure droppingfunnel, and mixed uniformly. The intermediate M3 above was then addedinto the flask to react at room temperature until the vibrational peakof isocyanate (2270 cm⁻¹) was disappeared. After distillation under areduced pressure, a dimercapto-capped thiourethane prepolymer (theproduct A2) in white powder was obtained.

FIG. 4 is an infrared vibration spectrum of the monomer A2. In FIG. 4,the peaks at 3311 cm⁻¹ and 1697 cm⁻¹ are vibrational peaks of urethanegroup and thiourethane group, respectively. The peak at 2536 cm⁻¹ is thevibrational peaks of thiol group. The peaks of 1600 cm⁻¹, 1531 cm⁻¹ and1474 cm⁻¹ are characteristic peaks of benzene ring. The peak at 814 cm⁻¹is the bending vibrational peaks of hydrogen attached to substitutedbenzene. Therefore, it can be known that the dimercapto-cappedthiourethane prepolymer A2 was synthesized.

Embodiment 4 Synthesising Sulfur-Containing Acrylate Oligomer C1 byA1→B1

16.8 g (0.02 mol) of the monomer B1 and 30 mL of THF was added in aflask equipped with a thermometer and a constant pressure droppingfunnel. After uniformly mixing, a solution of 9.38 g (0.01 mol) of themonomer A1, 0.026 g (0.1 wt %) of triethyl amine, and 20 mL of THF wasdropwise added into the flask. The reaction was performed at roomtemperature until the vibrational peak of thiol group at 2553 cm⁻¹ inthe IR spectrum was disappeared. After distillation under a reducedpressure, a white semi-solid product (i.e. sulfur-containing acrylateoligomer C1) was obtained. The chemical structure of thesulfur-containing acrylate oligomer C1 is B1¹-A1²-B1¹, wherein the A1²and B1¹ respectively have the chemical structure below.

FIG. 5 is an infrared vibration spectrum of the sulfur-containingacrylate oligomer C1. In FIG. 5, the peaks at 3339 cm⁻¹ and 1734 cm⁻¹are corresponding to the characteristic absorption peaks the urethanegroup, thiourethane group, and carbonyl group of the acrylate group.1600 cm⁻¹, 1531 cm⁻¹ and 1474 cm⁻¹ are the characteristic skeletonvibrational peaks of benzene ring. The peak at 1410 cm⁻¹ is thecharacteristic absorption peak of the double bong of acrylate group. Thepeak at 815 cm⁻¹ is corresponding to the characteristic absorption peakof the acrylate double bond and the bending vibrational peaks ofhydrogen attached to substituted benzene.

FIG. 6 is a ¹H nuclear magnetic resonance spectrum of thesulfur-containing acrylate oligomer C1. The chemical shifts at 6.88-7.88ppm are the peaks of hydrogen on benzene ring. The chemical shifts at5.90-6.60 ppm are the peaks of the acrylate double bond. The chemicalshifts at 4.31-4.41 ppm are the peaks of the methylene group next theester group (—CH₂—OCO—). The chemical shifts at 4.04-4.19 ppm are thepeaks of the methylene group next to the tertiary carbon and the estergroup (—C(CH₂O)₃—OCO). The chemical shift at 3.27 ppm is the peak of themethylene group of the thioether group (—S—CH₂—COO—). The chemicalshifts at 2.68 ppm and 2.90 ppm are the methylene group next to thethioether group (—S—CH₂—CH₂—CO—). Therefore, it can be known that theproduct of this embodiment is the sulfur-containing acrylate oligomercontaining 4 acrylate groups.

Embodiment 5 Synthesizing sulfur-containing acrylate dendrimer D1 byA1→B1

The preparation method was basically the same as the embodiment 4. Theonly difference is the added amount of the monomer B1 is 12.6 g (0.015mol).

Embodiment 6 Synthesizing Sulfur-Containing Acrylate Dendrimer D2 byA1→B1

The preparation method was basically the same as the embodiment 4. Theonly difference is the added amount of the monomer B1 is 10.08 g (0.012mol).

Embodiment 7 Synthesizing Sulfur-Containing Acrylate Dendrimer D3 byB1→A1

In a flask equipped with a thermometer and a constant pressure droppingfunnel, 9.38 g (0.01 mol) of monomer A1 and 30 mL of THF were added.After uniformly mixing, a solution of 16.8 g (0.02 mol) of monomer B1,0.026 g (0.1 wt %) of triethyl amine, and 20 mL of THF was then addedand reacted under room temperature until the thiol vibrational peak at2553 cm⁻¹ was disappeared in the IR spectrum. A white semi-solid product(i.e. the dendrimer D3) was obtained by distillation under a reducedpressure.

Embodiment 8 Synthesizing Sulfur-Containing Acrylate Dendrimer D4 byB1→A1

The preparation method was basically the same as the embodiment 7. Theonly difference is the added amount of the monomer B1 was 12.6 g (0.015mol).

Embodiment 9 Synthesizing Sulfur-Containing Acrylate Dendrimer D5 byB1→A1

The preparation method was basically the same as the embodiment 7. Theonly difference is the added amount of the monomer B1 was 10.08 g (0.012mol).

Embodiment 10 Synthesizing Sulfur-Containing Acrylate Oligomer C2 byA2→B1

In a flask equipped with a thermometer and a constant pressure droppingfunnel, 16.8 g (0.02 mol) of the monomer B1 and 20 mL of THF were addedand mixed. Then, a solution of 10.34 g (0.01 mol) of the monomer A2,0.027 g (0.1 wt %) of triethyl amine and 20 mL of THF was added andreacted at room temperature until the thiol vibrational peak at 2536cm⁻¹ was disappeared in the IR spectrum. A white semi-solid product(i.e. the oligomer C2) was obtained by distillation under a reducedpressure. The chemical structure of the sulfur-containing acrylateoligomer C2 is B1¹-A2²-B1¹, wherein the A2² and B1¹ respectively havethe chemical structure shown below.

FIG. 7 is an infrared vibration spectrum of the sulfur-containingacrylate oligomer C2. In FIG. 7, the peaks at 3335 cm⁻¹ and 1733 cm⁻¹are corresponding to the characteristic vibrational peaks of theurethane group, thiourethane group, and the carbonyl group of theacrylate group. 1521 cm⁻¹ and 1470 cm⁻¹ are the characteristic skeletonvibrational peaks of benzene ring. The peak at 1408 cm⁻¹ is thecharacteristic absorption peak of the double bong of acrylate group. Thetwin peaks at 1100-1300 cm⁻¹ are corresponding to the characteristicvibrational peak of the thioether group. The peak at 813 cm⁻¹ iscorresponding to the characteristic absorption peak of the acrylatedouble bond and the bending vibrational peaks of hydrogen attached tosubstituted benzene.

FIG. 8 is a ¹H nuclear magnetic resonance spectrum of thesulfur-containing acrylate oligomer C2. In FIG. 8, the chemical shiftsat 6.88-7.88 ppm are the peaks of hydrogen on benzene ring. The chemicalshifts at 5.90-6.60 ppm are the peaks of the acrylate double bond. Thechemical shifts at 4.31-4.41 ppm are the peaks of the methylene groupnext the ester group (—CH₂—OCO—). The chemical shifts at 4.04-4.19 ppmare the peaks of the methylene group next to the tertiary carbon and theester group (—C(CH₂O)₃—OCO). The chemical shift at 3.27 ppm is the peakof the methylene group of the thioether group (—S—CH₂—COO—). Thechemical shifts at 2.68 ppm and 2.90 ppm are the methylene group next tothe thioether group (—S—CH₂—CH₂—CO—). Therefore, it can be known thatthe product of this embodiment is the sulfur-containing acrylateoligomer containing 4 acrylate groups.

Embodiment 11 Synthesizing sulfur-containing acrylate dendrimer D6 byA2→B1

The preparation method was basically the same as the embodiment 10. Theonly difference is the added amount of the monomer B1 is 12.6 g (0.015mol).

Embodiment 12 Synthesizing sulfur-containing acrylate dendrimer D7 byA2→B1

The preparation method was basically the same as the embodiment 10. Theonly difference is the added amount of the monomer B1 is 10.08 g (0.012mol).

Embodiment 13 Synthesizing sulfur-containing acrylate dendrimer D8 byB1→A2

In a flask equipped with a thermometer and a constant pressure droppingfunnel, 10.34 g (0.01 mol) of monomer A2 and 30 mL of THF were added.After uniformly mixing, a solution of 16.8 g (0.02 mol) of monomer B1,0.026 g (0.1 wt %) of triethyl amine, and 20 mL of THF was then addedand reacted under room temperature until the thiol vibrational peak at2553 cm⁻¹ was disappeared in the IR spectrum. A white semi-solid product(i.e. the dendrimer D8) was obtained by distillation under a reducedpressure.

Embodiment 14 Synthesizing Sulfur-Containing Acrylate Dendrimer D9 byB1→A2

The preparation method was basically the same as the embodiment 13. Theonly difference is the added amount of the monomer B1 is 12.6 g (0.015mol).

Embodiment 15 Synthesizing Sulfur-Containing Acrylate Dendrimer D10 byB1→A2

The preparation method was basically the same as the embodiment 13. Theonly difference is the added amount of the monomer B1 is 10.08 g (0.012mol).

Embodiment 16 Cross-Linking the Sulfur-Containing Acrylate Oligomer andDendrimer by UV Light

The sulfur-containing acrylate oligomer C1 and C2 above (embodiments 4and 10) were respectively mixed with 1.5 wt % of a photoinitiator,2-hydroxy-2-methyl-1-phenyl-propan-1-one (Iragcure 1173; RUNTEC ChemicalCo. Ltd.). The mixture was then coated on a quartz glass (1 mm thick andwith a refractive index of 1.514) or a tin plate (50 mm×120 mm×0.3 mm)to form a thin film having a thickness of 200 μm. A medium pressuremercury lamp (F300S-6 from Fusion UV Systems, US) was used to illuminatethe thin films at a distance of 10 cm to cross link the oligomer C1 orC2. Finally, a hard transparent cross-linked thin film was obtained.

The sulfur-containing acrylate dendrimer D1-D10 (embodiments 5-9 and11-15) was also cross-linked by the method described above.

The refractive index (on the quartz glass), pencil hardness (on the tinplate), flexibility (on the tin plate), impact toughness (on the tinpate) of the oligomers C1 and C2, and the dendrimers D1-D10 wererespectively measured and then listed in the table 1 below.

TABLE 1 Physical properties of oligomers C1 and C2, and the dendrimersD1-D10 Molar Flexi- Impact Addition ratio Refractive Pencil bilitytough- samples method B/A index ^(a) hardness ^(b) (mm) ^(c) ness ^(d)C1 A1 →B1 2 1.5941 5H <2 ◯ D1 1.5 1.6035 5H <2 ◯ D2 1.2 1.6083 4H <2 ◯D3 B1 →A1 2 1.5924 5H <2 ◯ D4 1.5 1.5966 5H <2 ◯ D5 1.2 1.6037 4H <2 ◯C2 A2 →B1 2 1.5764 5H <2 ◯ D6 1.5 1.5792 4H <2 ◯ D7 1.2 1.5840 4H <2 ◯D8 B1 →A2 2 1.5753 5H <2 ◯ D9 1.5 1.5786 4H <2 ◯ D10 1.2 1.5840 4H <2 ◯CE — — 1.4900 3H 5 X ^(a) measured at 632.8 nm by a prism coupler (PRISMCOUPLER SPA-4000, Korea) ^(b) measured by a pencil hardness tester(model QHQ-A, Tinjinshi Jinkekecailiao shiyanjichang, China) andfollowing the standard of GB6739-1996 ^(c) measured by a flexibilityinstrument (model QTX, Tinjinshi Jinkekecailiao shiyanjichang, China)and following the standard of GBT1731-1993 ^(d) measured by impacttoughness instrument (model QCY, Tinjinshi Jinkekecailiao shiyanjichang,China) and following the standard of GBT1732-1993

Furthermore, a comparative example (CE) was also prepared. In thiscomparative example, a monomer of methylmethacrylate (EM31 from EternalChemical, Taiwan) was coated on the quartz glass and the tin plate, andthen cross-linked by UV light by the method described above,respectively. Finally, a layer of polymethylmethacrylate (PMMA) wasobtained. The refractive index, pencil hardness, flexibility, impacttoughness of the PMMA layer was also measured.

According to the results shown in the table 1 above, the refractiveindex of the oligomers C1 and C2, and dendrimers D1-D10 were all above1.5, and greater than the refractive index of the comparative example.Therefore, the oligomers C1 and C2, and dendrimers D1-D10 all have highrefractive indexes.

Embodiment 17 Modification of the Sulfur-Containing Acrylate Oligomer

In a flask equipped with thermometer, and a constant pressure droppingfunnel, n equivalent number of sulfur-containing acrylate oligomer C1 orC2, and THF were added and mixed. The n equivalent number ofsulfur-containing acrylate oligomer C1 or C2 contains 4n equivalentnumber of unreacted acrylate group. A solution of 2n equivalent numberof a thiol-containing modifier, 0.1 wt % of triethyl amine, and THF wasthen dropwise added to the flask and then underwent Michael addition atroom temperature until the vibrational peak of thiol group (2528 cm⁻¹)was disappeared in the IR spectrum. A semi-solid white solid, i.e. themodified oligomer C1′ or C2′, was obtained after distilling under areduced pressure. The thiol-containing modifier was2-mercaptobenzothiazole, 2-mercapto-2-thiazoline, or2-mercapto-5-methyl-1,3,4-thiadiazole, which are all from XiaoGanShenYuan Chemical Co., LTD.

From the IR spectrum analysis of the modified sulfur-containing acrylateoligomer C1′ or C2′, it can be known that the thiol-containing modifiershad successfully modified the sulfur-containing acrylate oligomer C1 orC2.

Embodiment 18 Modification of the Sulfur-Containing Acrylate Dendrimer

In a flask equipped with thermometer, and a constant pressure droppingfunnel, the sulfur-containing acrylate dendrimer D3 or D8, whichcontains 2 equivalent numbers of unreacted acrylate groups, and THF wereadded and mixed. A solution of 0.8n equivalent number of athiol-containing modifier, 0.1 wt % of triethyl amine, and THF was thendropwise added to the flask and then underwent Michael addition at roomtemperature until the vibrational peak of thiol group (2528 cm⁻¹) wasdisappeared in the IR spectrum. A semi-solid white solid, i.e. themodified dendrimer D3′ or D8′, was obtained after distilling under areduced pressure. The thiol-containing modifier was2-mercaptobenzothiazole, 2-mercapto-2-thiazoline, or2-mercapto-5-methyl-1,3,4-thiadiazole.

From the IR spectrum analysis of the modified sulfur-containing acrylatedendrimer D3′ or D8′, it can be known that the thiol-containingmodifiers had successfully modified the sulfur-containing acrylatedendrimer D3 or D8.

Embodiment 19 Cross-Linking the Modified Sulfur-Containing AcrylateOligomer or Dendrimer

The modified sulfur-containing acrylate oligomer C1′ and C2′, and themodified sulfur-containing acrylate dendrimer D3′ and D8′ wererespectively added with a photoinitiator,2-hydroxy-2-methyl-1-phenyl-propan-1-one (Iragcure 1173; RUNTEC ChemicalCo. Ltd.). The mixture was then coated on a quartz glass (1 mm thick andwith a refractive index of 1.514) to form a thin film having a thicknessof 200 μm. A medium pressure mercury lamp (F300S-6 from Fusion UVSystems, US) was used to illuminate the thin films at a distance of 10cm to cross link the oligomer C1 or C2. Finally, a hard transparentcross-linked thin film was obtained. The measured refractive index ofthe modified oligomers C1′ and C2′ and the modified dendrimer D3′ andD8′ are listed in the table 2 below.

From the results listed in table 2, it can be known that the refractiveindex of the sulfur-containing acrylate oligomer and dendrimer can befurther increased by the thiol-containing modifier. In addition, sincethe number of the unreacted acrylate functional group was decreased, thestorage stability and the thermal stability can be further increased.Therefore, the modified oligomers and dendrimers are especially suitableto be used in the high-temperature applications, such as thermal bondingand high-temperature coatings.

TABLE 2 Properties test of the modified sulfur-containing acrylateoligomer or dendrimer Refractive Molar ratio Sample modifier index*B1/A1 = 2 Oligomer C1′

1.6085

1.6032

1.6013 Dendrimer D3′

1.6198

1.6065

1.6027 B1/A2 = 2 Oligomer C2′

1.5910

1.5855

1.5832 Dendrimer D8′

1.6062

1.5935

1.5920 *measured at 632.8 nm by a prism coupler (PRISM COUPLER SPA-4000,Korea)

From the disclosure above, the advantage of this invention include thefollowings.

1. The reaction materials of the sulfur-containing acrylate oligomersand dendrimers are cheap, easily obtained, and not strong corrosive andirritating.

2. The preparation conditions of the sulfur-containing acrylateoligomers and dendrimers are mild, and fewer side reaction and almost nobyproducts. Therefore, the preparations are less pollution, high yield,and stable product quality. Hence, the preparation conditions are easyto be controlled, and easy to be applied in industry.

3. The viscosity of the obtained sulfur-containing acrylate dendrimersis small and hard to be gelled, and thus the dendrimers have advantagesof better storage and coating. When using the composition containing thedendrimers as a coating material, the obtained sulfur-containingacrylate oligomers can be used as diluents of the sulfur-containingacrylate dendrimers. Therefore, if the viscosity of thesulfur-containing acrylate dendrimers is too large, only a small amountof a sulfur-containing acrylate oligomer is needed to be added into thedendrimer to effectively maintain the refractive index and themechanical properties of the composition with dendrimers.

4. The cross-linking reaction of the sulfur-containing acrylateoligomers and dendrimers has the advantages of low energy consumption,fast cross-linking rate, low amount of organic volatiles, and goodfilm-formation.

5. The cross-linked thin film of the sulfur-containing acrylateoligomers and dendrimers have higher refractive index, bettertransparency, higher hardness, better flexibility and stronger impacttoughness.

All the features disclosed in this specification (including anyaccompanying claims, abstract, and drawings) may be replaced byalternative features serving the same, equivalent or similar purpose,unless expressly stated otherwise. Thus, each feature disclosed is oneexample only of a generic series of equivalent or similar features.

What is claimed is:
 1. A sulfur-containing acrylate oligomer having achemical structure of B¹-A²-B¹, wherein A² and B¹ respectively havechemical structures below:

and wherein R₁, R₄, R₅ and R₆ are respectively an alkyl group with 1-6carbons, and R₂ and R₃ are respectively an aromatic or a cycloalkylgroup.
 2. The sulfur-containing acrylate oligomer of claim 1, whereinthe R₂ and the R₃ respectively have a chemical structure of


3. The sulfur-containing acrylate oligomer of claim 1, wherein the R₁and R₄ are respectively a straight chain alkyl group having 1-4 carbons.4. The sulfur-containing acrylate oligomer of claim 1, wherein the R₅and R₆ are respectively a straight chain alkyl group having 2, 4, or 6carbons.
 5. The sulfur-containing acrylate oligomer of claim 1, whereinA² is


6. The sulfur-containing acrylate oligomer of claim 1, wherein B¹ is


7. A modified sulfur-containing acrylate oligomer having a chemicalstructure of B¹′-A²-B¹′, B¹′-A²-B¹″ or B¹″-A²-B¹″, wherein A², B¹′ andB¹″ respectively have the chemical structures below:

and wherein R₁, R₄, R₅ and R₆ are respectively an alkyl group with 1-6carbons, R₂ and R₃ are respectively an aromatic or a cycloalkyl group,and R₇ is an aromatic group or a heterocyclic group having at least adouble bond.
 8. A method of preparing a sulfur-containing acrylateoligomer, the method comprising: dropwise adding a monomer A into anaprotic solvent containing a monomer B to perform Michael addition toobtain a sulfur-containing acrylate oligomer, wherein the molar ratio ofA to B is 1:2, and A and B respectively have chemical structures below:

wherein the sulfur-containing acrylate oligomer having a chemicalstructure of B¹-A²-B¹, wherein A² and B¹ respectively have chemicalstructures below, and R₁, R₄, R₅ and R₆ are respectively an alkyl groupwith 1-6 carbons, and R₂ and R₃ are respectively an aromatic or acycloalkyl group.


9. The method of claim 8, further comprising adding a catalyst to theaprotic solvent to catalyze the Michael addition.
 10. A method ofpreparing a modified sulfur-containing acrylate oligomer, the methodcomprising: dropwise adding a monomer A into an aprotic solventcontaining a monomer B to perform Michael addition to obtain asulfur-containing acrylate oligomer, wherein the molar ratio of A to Bis 1:2, and A and B respectively have chemical structures below:

wherein the sulfur-containing acrylate oligomer having a chemicalstructure of B¹-A²-B¹, wherein A² and B¹ respectively have chemicalstructures below, and R₁, R₄, R₅ and R₆ are respectively an alkyl groupwith 1-6 carbons, and R₂ and R₃ are respectively an aromatic or acycloalkyl group; and

adding a thiol-containing modifier (R₇SH) to perform Michael additionwith the sulfur-containing acrylate oligomer to obtain a modifiedsulfur-containing acrylate oligomer having a chemical structure ofB¹′-A²-B¹′, B¹′-A²-B¹′, or B¹″-A²-B¹″, wherein B¹′ and B¹″ respectivelyhave the chemical structures below, and R₇ is an aromatic group or aheterocyclic group having at least a double bond.


11. A sulfur-containing acrylate dendrimer having a chemical structureof

wherein B¹ and B² are randomly distributed on terminals of thesulfur-containing acrylate dendrimer, and the chemical structures of A²,B¹, B² and B³ are shown below:

and wherein R₁, R₄, R₅ and R₆ are respectively an alkyl group with 1-6carbons, and R₂ and R₃ are respectively an aromatic or a cycloalkylgroup.
 12. The sulfur-containing acrylate dendrimer of claim 11, whereinthe R₂ and the R₃ respectively have a chemical structure of


13. The sulfur-containing acrylate dendrimer of claim 11, wherein the R₁and R₄ are respectively a straight chain alkyl group having 1-4 carbons.14. The sulfur-containing acrylate dendrimer of claim 11, wherein the R₅and R₆ are respectively a straight chain alkyl group having 2, 4, or 6carbons.
 15. The sulfur-containing acrylate dendrimer of claim 11,wherein A² is


16. The sulfur-containing acrylate dendrimer of claim 11, wherein B¹,B²and B³ are

respectively.
 17. A modified sulfur-containing acrylate dendrimer havinga chemical structure of

wherein A², B¹′, B¹″, B²′ and B³ respectively have chemical structuresbelow:

and wherein R₁, R₄, R₅ and R₆ are respectively an alkyl group with 1-6carbons, R₂ and R₃ are respectively an aromatic or a cycloalkyl group,and R₇ is an aromatic group or a heterocyclic group having at least adouble bond.
 18. A method of preparing a sulfur-containing acrylatedendrimer, the method comprising: reacting a monomer A and a monomer Bin an aprotic solvent to obtain a sulfur-containing acrylate dendrimerhaving a chemical structure of

wherein B¹ and B² are randomly distributed on terminals of thesulfur-containing acrylate dendrimer, wherein the molar ratio of monomerA to monomer B is 1:0.25-4, but not 1:2 when the monomer A is added tothe aprotic solvent containing the monomer B, and the monomer A, monomerB, A², B¹, B² and B³ respectively have chemical structures below:

wherein R₁, R₄, R₅ and R₆ are respectively an alkyl group with 1-6carbons, and R₂ and R₃ are respectively an aromatic or a cycloalkylgroup.
 19. The method of claim 18, further comprising adding a catalystto the aprotic solvent to catalyze the reaction.
 20. A method ofpreparing a modified sulfur-containing acrylate dendrimer, the methodcomprising: reacting a monomer A and a monomer B in an aprotic solventto obtain a sulfur-containing acrylate dendrimer having a chemicalstructure of

wherein B¹ and B² are randomly distributed on terminals of thesulfur-containing acrylate dendrimer, wherein the molar ratio of monomerA to monomer B is 1:0.25-4, but not 1:2 when the monomer A is added tothe aprotic solvent containing the monomer B, and the monomer A, monomerB, A², B¹, B² and B³ respectively have chemical structures below:

wherein R₁, R₄, R₅ and R₆ are respectively an alkyl group with 1-6carbons, and R₂ and R₃ are respectively an aromatic or a cycloalkylgroup; and adding a thiol-containing modifier (R₇SH) to perform Michaeladdition with the sulfur-containing acrylate dendrimer to obtain amodified sulfur-containing acrylate dendrimer having a chemicalstructure of

wherein B¹′, B¹″, and B²′ respectively have chemical structures below:

and wherein R₇ is an aromatic group or a heterocyclic group having atleast a double bond.